Supreme Detail Page : Looking for use default photo for each place of each cat

Hello everybody,

> Theme Supreme
> On the detail page

I would like to use a unique photography on the banner of the detail page (the default photo of the category) for all the posts, even if each post has a gallery photo.

However, I want to keep the first photo of my gallery in the listing page, in order to differenciate the different posts.

Indeed, on the detail page, when the photography banner is downloaded, I have problem of px because of the quality of the photos that I can’t change.
That’s why I would like to use the unique default photo category, with a lot of px.

Is it possible, Is there a setting or a trick ?

Thank you very much,

Cyrille